Very nicely put together article. Your graphic for the sail plan was fantastic. The only thing I can't figure out on it is why there are three jib sheets? There seems to be an active and lazy sheet on the starboard side. Why is this?
Then only thing I can think is that you want to keep your "upwind jib lead" threaded and also run a sheet back through an aft turning block to get a better angle. Once you fix the clew position with the pole, though, the sheeting angle doesn't really matter anymore, does it?
Well, I won't presume to speak for Pete, but I think it's a good idea to use a separate, somewhat 'sacrificial' sheet, to eliminate the possibility of chafing what might be a high quality/very expensive rope being used for the jib sheets...
Chafe at the pole end isn't much of an issue as long as the clew if butted right up against the jaw of the pole, but if you wind up furling the sail a bit while using a fixed length pole, then chafe can certainly become a problem on a long, rolly passage...
Your guess about the jib sheeting angle is a good one, as well... Always depends on the boat, of course, but on a boat with a jib not much larger than 100%, normally sheeting inboard of the shrouds, perhaps, the angle of the lead back inboard to the car can be a bit sharp. That will also increase the compression forces on the pole, never a good thing, particularly if using an adjustable line-control pole... Taking the lead back to a snatch or turning block back at the cockpit is just a bit easier all around, and reduces the load on the pole at least somewhat, and makes the sail a bit easier to trim if being unfurled, or the pole brought further aft...